New conjugated polyenes with 1,3-dialkyl-2-thiobarbituric acid moiety as materials for nonlinear optics: theoretical calculations, synthesis and spectral properties

In this work we report the results of our study on electronic and spectral properties of conjugated polyenes with electron-accepting 1,3-dialkyl-2-thiobarbituric acid moiety. In model calculations, we examine the effect of the conjugated polyene length on infrared (IR) and Raman spectra of the polyenes by means of ab initio HF/3-21G*. Nonlinear properties were also studied by AM1 method in frames of the sum-over-states (SOS) and finite-field formalism. It was concluded that in well-resolved IR and Raman spectra the frequencies and band intensities can provide valuable information relating to C=C bond lengths in polyene chain and relative polarizabilities. Near-linear correlation between polarizability and integral IR band intensity, corresponding to all C=C stretching modes, and the rather nonlinear relationship of polarizability with integral Raman activity, was found. In our calculation we predict that polarizability and the first hyperpolarizability increases with elongation of polyene chain while the second hyperpolarizability increases smoothly in a quadratic way. In contrast to the linear relationship between polarizability and polyene chain length the dipole moment versus chain length is predicted to be nonlinear. A good agreement was found between experimental and calculated Raman spectra of one newly synthesized compound studied.     

中药常山中的常山碱其电子结构和光谱性质的理论研究

用ZINDO、从头算、密度泛函和含时密度泛函理论法,研究常山碱的电子结构和光谱性质.模拟α-常山碱和β-常山碱的吸收光谱和荧光光谱成功,利用电荷密度差(CDD)和前线分子轨道(FMO)的组成,分析电子跃迁的特征,将每个吸收光谱和荧光光谱峰归属,发现α-常山碱和β-常山碱的吸收光谱均发生在母核4-喹唑酮上,而其荧光光谱则与母核4-喹唑酮和N3连接的基团有关.量子化学计算法可用来研究这类化合物的定性和定量.     

Theoretical investigation on second-order nonlinear optical properties of ruthenium alkynyl–dihydroazulene/vinylheptafulvene complexes

Ru metal acetylide electron donor-acceptor complexes have important applications in the field of nonlinear optics. Herein, in this work, a series of half-sandwich ruthenium-based Cp*(dpe)Ru ([Ru*]) metal complexes with the dihydroazulene/vinylheptafulvene (DHA/VHF) have been investigated by density functional theory (DFT) calculations. The results showed that the position of the [Ru*] acetylide functionality, either para or meta on the phenylene ring to the DHA/VHF core (1c/1o and 2c/2o), and additional a p-phenylene spacer (3c/3o) had a great influence on the second-order nonlinear optical (NLO) responses. The systems 1 and 3 can significantly increased second-order NLO responses compared with system 2. It was attributed to the more obvious charge transfer along y-axis, which is from [Ru*] acetylide functionality to DHA, accompanied by a significant decrease of the transition energy according electron density difference maps and time-dependent DFT calculations. The β_vec values of the open-ring complexes were larger than the corresponding closed-ring complexes owing to the smaller HOMO−LUMO gap in the open-ring complexes. It was also because of the smaller BLA values in open-ring complexes, which had stronger π-conjugation. Especially, the change ratio of β_vec value of system 2 was the largest due to the fact that their charge transfers degree varied greatly. In addition, the frequency-dependent NLO properties of the studied complexes were evaluated at 0.0239 a.u. and 0.0340 a.u. The calculation results demonstrated that the magnitude of the frequency-dependent first hyperpolarizability increased with the increasing frequency. We believe that our present work will be beneficial for further theoretical and experimental studies on large second-order NLO responses of metal complexes.     

L-Thr-TPPMg电子结构及光谱性质的理论研究

采用密度泛函理论方法在B3LYP和混合基组(C、H原子采用6-31G(d);Mg、N、O采用6-311++G(2d,p))水平对含L-苏氨酸侧链的四苯基卟啉镁衍生物L-Thr-TPPMg的基态几何构型进行了优化,获得了稳定的分子构型。以获得的稳定构型为基础,在相同基组水平进行了红外吸收光谱研究;采用含时密度泛函理论方法,在相同基组水平进行了紫外吸收光谱和电子圆二色谱研究。理论研究发现:(1)L-苏氨酸的羧基氧原子与镁原子之间存在配位作用。(2)氮镁配位键、氧镁配位键的伸缩振动在IR谱中的1022 cm~(-1)、278 cm~(1)处呈现特征吸收峰。(3)理论UV谱存在Soret带和Q带吸收。Q带吸收峰主要由HOMO→LUMO的荷移跃迁贡献;Sorer带的吸收峰主要由HOMO-1→LUMO的荷移跃迁贡献。(4)Sorct区表现出分裂的ECD谱。第1 Cotton效应主要来源于分子由HOMO-1→LUMO的荷移跃迁;第2 Cotton效应主要由HOMO-1→LUMO+1的荷移跃迁贡献。上述跃迁均为π→π~*的荷移跃迁。     

An empirical investigation of a modified technology acceptance model of IPTV

This study explores the factors influencing the adoption of IPTV, and tests the applicability of the technology acceptance model (TAM) in a new convergent technology. The behavioural constructs from TAM were tested for predicting user acceptance of IPTV. Structural equation modelling was used to analyse data and to design a theoretical model predicting the individual's intention to adopt IPTV. A modified TAM for IPTV proposes that new constructs determine user-perceived usefulness and enjoyment of using IPTV. Although this study confirms the impact of information quality and system quality on consumers' technology experience, it specifically shows that the perceived quality of content and system were found to have a significant effect on users' perceived usefulness and perceived enjoyment. In addition, social influences had a positive effect on the intention to use IPTV. These findings suggest an extension of the TAM model for convergence technologies. This research advances theory and contributes to the foundation for future research aimed at improving the understanding of users' adoption behaviour of convergence technologies. Implications of these findings for practice and research are examined.     

Dynamical properties of an adaptive control system with a nonlinear reference model. II

We consider the problem of constructing an adaptive control system with nonlinear reference model for a low order nonstationary dynamical object with a nonlinear actuator. We show the structure, analysis, and mathematical modeling results for the adaptive control system.     

Dynamical properties of an adaptive control system with a nonlinear reference model. I

We show the results of solving the problem of constructing an adaptive control system with nonlinear reference model for a nonstationary dynamical object with a nonlinear actuator. To analyze the dynamical properties of a nonlinear nonstationary control system we use the method of pointwise transformations. We show the results of analysis and mathematical modeling of the considered control system with the adaptation circuit switched off.     

Third-order nonlinear optical properties of molecules containing aromatic diimides: Effects of the aromatic core size and a redox-switchable modification

The third-order nonlinear optical (NLO) properties of aromatic diimide molecules have been studied for the first time using density functional theory (DFT) with a finite field (FF). This study shows that the size of the aromatic core can affect the static second hyperpolarizability (γ). Increasing the number of benzenes along the longitudinal axis can effectively improve the γ values because the degree of charge transfer along the longitudinal direction increases, whereas an increase in the number of benzenes along the perpendicular axis does not enhance the γ values. Furthermore, the NLO responses of the reduced form radical anions 1⁻, 5⁻ and 6⁻, which were obtained by a reversible redox process, are discussed. The results show that the γ values of the radical anions are changed by the redox process. For the reduced form radical anion 6⁻, the γ value is −1906.71 × 10⁻³⁶ esu, and its absolute value is ∼7.3 times larger than that of its neutral parent. An analysis of the BLA values demonstrates that the γ value is closely related to the conjugation of the aromatic core used in the redox process.     

Control of discrete time nonlinear systems with a time-varying structure

In this paper, we present a control methodology for a class of discrete time nonlinear systems that depend on a possibly exogenous scheduling variable. This class of systems consists of an interpolation of nonlinear dynamic equations in strict feedback form, and it may represent systems with a time-varying nonlinear structure. Moreover, this class of systems is able to represent some cases of gain scheduling control, Takagi-Sugeno fuzzy systems, as well as input-output realizations of nonlinear systems which are approximated via localized linearizations. We present two control theorems, one using what we call a “global” approach (akin to traditional backstepping), and a “local” approach, our main result, where backstepping is again used but the control law is an interpolation of local control terms. An aircraft wing rock regulation problem with varying angle of attack is used to illustrate and compare the two approaches.     

煤基富勒烯电子性质和非线性光学性质的密度泛函理论研究

使用基于密度泛函理论的量子化学计算方法对煤基富勒烯进行了研究。重点关注由氮和硅掺杂C₆₀形成的杂化富勒烯结构。计算了这些杂化富勒烯的几何结构、稳定性、电子结构、介电常数和非线性光学性质并与未掺杂富勒烯相比较。研究发现,氮掺杂富勒烯失电子能力增强而硅掺杂富勒烯得电子能力增强。此外,根据计算结果可知掺杂可使富勒烯介电常数增大。对煤基富勒烯的非线性光学性质进行了探讨,发现氮掺杂富勒烯和硅掺杂富勒烯均具有比未掺杂富勒烯明显大的三阶非线性光学系数。     

苯甲基阴离子复合物结构与性质的理论研究

用G98程序在B3LYP和MP2方法上和理论上计算苯…甲基阴离子复合物以预测其构型,得4种.在考虑基组重叠误差校正基础上,得结合能,并用自然键轨道分析法讨论其相互作用.结果表明,甲基阴离子中C13与苯中的一个C原子直接相连的构型比较稳定,其结合能为-108.45 kJ/mol(B3LYP/6-31+G*)、-154.1 kJ/mol(MP2(FC)/6-311++G**).其余的构型靠碳的孤对电子与C-Hσ反键轨道作用而形成,且稳定性较差.     

Computational study of structural,optoelectronic and nonlinear optical properties of dynamic solid-state chalcone derivatives

In the present study, we use the state of art density functional theory (DFT) techniques to calculate the structural, optoelectronic and nonlinear optical (NLO) properties for two novel chalcone derivatives. The geometrical structures of chalcone derivatives compound 1 and 2 are optimized using periodic boundary conditions (PBC) in solid-state phase as well as isolated single molecular geometry in the gas phase. The reasonable agreement is found among experimental, solid-state and gas phase single molecular geometries, which provide us, further confidence to explore the potential of above-entitled derivatives as good functional materials for electro-optical applications. For instance, the frequency dependent real parts of dielectric functions are calculated for compound 1 and 2. The maximum value of real part of the dielectric function for compound 1 and 2 at 0 eV are computed as 4.35 and 6.68 for the polarization vectors of (001) directions, respectively, which reveals the fact that the compound 1 and 2 might be good charge transport materials. The reflectivities of the compound 1 and 2 are 0.64 and 0.45 revealing that the compound 2 might be more efficient material for organic photovoltaic (OPV) applications. The results of the refractive index improved by doping the strong electron withdrawing groups (EWGs) shows that the compound 2 might be good refractor of the photon as compared to compound 1. The calculated values for static second-order polarizability are 3498 and 10464 a. u. and for frequency dependent second harmonic generations are 2557 and 6429 a. u. for compound 1 and 2, respectively, which indicates their significant potential for possible nonlinear optical applications.     

Hybrid explicit model predictive control of a nonlinear process approximated with a piecewise affine model

The recently developed methods of explicit (multi-parametric) model predictive control (e-MPC) for hybrid systems provide an interesting opportunity for solving a class of nonlinear control problems. With this approach, the nonlinear process is approximated by a piecewise affine (PWA) hybrid model containing a set of local linear dynamics. Compared to linear-model-based MPC, a performance improvement is expected with the reduction of the plant-to-model mismatch; however at a cost of controller computation complexity. In order to reduce the computational load, so that desired horizon lengths may be used, we present an efficient sub-optimal solution. The feasibility of the approach for the application was evaluated in an experimental case study, where an output feedback, offset-free-tracking hybrid e-MPC controller was considered as a replacement for a PID-controller-based scheme for the control of the pressure in a wire-annealing machine.     

Dynamic modeling and nonlinear tracking control of a novel modified quadrotor

In this article, a nonlinear tracking controller is designed based on Lyapunov stability for a novel aerial robot. The proposed 6‐rotor configuration improves stability and payload lifting capacity of the robot compared with conventional quadrotors while avoiding further complexities in the robot dynamics and steering principles. The dynamical model of the robot is derived using Newton‐Euler method. The model represents a nonlinear, coupled, and underactuated system. The proposed control strategy includes 2 main parts: an attitude controller and a position controller. Both the attitude and position controls are Lyapunov‐based nonlinear tracking controllers that guarantee the asymptotic convergence of the states' tracking errors to zero. Simulation results are presented to illustrate appropriate performance of the closed‐loop system in terms of position/attitude tracking even in the presence of wind disturbance.     

On global controllability of affine nonlinear systems with a triangular-like structure

In this paper, we investigate a class of affine nonlinear systems with a triangular-like structure and present its necessary and sufficient condition for global controllability, by using the techniques developed by Sun Yimin and Guo Lei recently. Furthermore, we will give two examples to illustrate its application.     

Learning associations between natural groups of input and output with a neurofuzzy structure

A new modeling approach that finds the associations between natural groups of input and output is proposed. In the new method, input and output are clustered separately by means of Fuzzy C-Means (FCM) algorithm. Then, the learning algorithm identifies the fuzzy rules by relating the resulting fuzzy sets in input and output spaces by using a neurofuzzy architecture. A modified version of classical simulated annealing algorithm is used in order to identify the relative weights of system input variables. The proposed approach is applied to a highly nonlinear function and successful result is achieved.     

Market structure and quality uncertainty: a theoretical framework for online auction research

Given large numbers of buyers and sellers, with access to a wide variety of information, economic theory suggests that online auction markets should provide an efficient mechanism for establishing equilibrium prices. Previous research on online auction prices, however, is far from conclusive, having produced mixed findings. The seemingly inconsistent and sometimes contradictory results make it very difficult to integrate empirical findings into a coherent body of knowledge. The purpose of this paper is to present a framework that can reconcile previous findings and provide direction for future research. Accordingly, we propose a simple theoretical framework with two dimensions—market structure (thick vs. thin) and quality uncertainty (high vs. low). By examining the literature in the context of market structure and quality uncertainty we find that previous studies are not necessarily at odds, but that there is actually a fairly consistent pattern of results.     

Cosmological models with nonlinear scalar and spinor fields simulating a generalized and modified Chaplygin gas

Cosmological models with a generalized and modified Chaplygin gas equivalent to nonlinear scalar and spinor fields have been considered. Scale factors and field potentials have been found.